Mobile devices such as portable computers, tablets, and smart phones can often be powered by a battery or an alternating current (AC) adapter. Preferably, if an AC adapter is plugged into a mobile device, the mobile device uses power from the AC adapter rather than the battery. If an AC adapter is not plugged into the mobile device, the mobile device uses power from the battery.
Today, the system power requirements of a mobile device may be such that more power is needed by the mobile device than the AC adapter can provide (even though it is a constant source of power when plugged into the mobile device). In some systems, when both the battery and the AC adapter are available, in order to provide the necessary power to the mobile device to meet its system power requirements, the mobile device receives power from both the AC adapter and the battery, where the battery power is supplementing the power provided by the AC adapter. This is referred to as power sharing.
However, in systems that use power sharing, there are times when the power output capacity of the AC adapter is greater than the system power requirement of the mobile device. In this case, the excess power capacity is used for charging of the battery.
A problem exists when using power sharing. Because the system power requirements of the mobile device are constantly changing, this power sharing causes repeated charging and discharging (e.g., sporadic charge/discharge) of the battery. The repeated charging and discharging impacts battery cycle life. Furthermore, repeating the charging and discharging of the battery in higher voltage ranges degrades the battery cycle life more than that in lower voltage ranges. That is, sporadic charging and discharging degrades battery cycle life especially when it occurs in a higher voltage range. Thus, while the use of power sharing has advantages, it can produce undesirable consequences.